A Simple Method of Bluing You Can Do At Home

As homebuilders, we all eventually come to the same point in a build, no matter what the build is; “Ok, it works. Now, what do I do for finishing?” These days there are quite a few options out there for firearm finishes. A lot of these are suitable for us DIY types. But, there are some guns that the modern spray-on finishes just do not look right on. Previously, I wrote an article on Parkerizing. But again, there are some guns that Parkerizing wouldn’t be an appropriate finish for either. Or maybe you just like the look of a nice blued finish on your firearms. This article is for just such occasions.

When we refer to bluing, we typically think of the hot salt bluing that is usually done. This process requires a lot of equipment that takes up a lot of space, and the process itself can be somewhat hazardous. Obviously, this doesn’t easily lend itself to the hobbyist homebuilder or “kitchen table gunsmith”. There are cold bluing solutions available as well. There are some that you can realistically do a bit more than just touch up work with. But even so, these are not really intended for bluing a whole firearm.

Here is the start of the project: a bare steel, Sten Mk. V barrel

That brings us to rust bluing. When bluing was first invented, this was how firearms were blued. Basically, a chemical rusting agent is applied to the steel, time passes, and rust forms. The rust is “polished off”. The steel has changed color slightly in this process, and the process is repeated until the steel is the desired color. The problem with this process is that it takes a REALLY long time. We literally are talking days or even weeks to complete. Fortunately, there is a similar but much faster process-Express Rust Bluing. As its name implies, Express Rust Bluing speeds up this whole process significantly.

Express Rust Bluing is faster than rust bluing because rather than allowing the chemical reaction to happen “naturally” the process is expedited by boiling the parts. So instead of having to wait for the parts to rust for a couple of days, you actually force them to form rust in a few minutes. This takes the process down to something you can do in an afternoon (as long as the parts are already prepped).

Some of the more astute of you reading this probably read the previous paragraph and went, “Wait, I’m supposed to allow it to rust?!” You would be correct. Rust, properly referred to as Iron Oxide, is FeO2. Bluing is FeO3 or rust with an extra oxygen molecule. This conversion happens as part of the chemical reaction to the rusting agent in the boiling tank. I’m not a chemist by any means, so I’m sure there’s a lot more to it than that. But I think you can get the gist.

For the hobbyist, there are a lot of advantages to this process. You don’t need a whole lot of equipment, or space. The chemical used is also fairly safe, especially in comparison to bluing salts. Express Rust Bluing is actually preferable on some types of firearms due to their construction because you have control where the bluing formula goes (and hence make sure it all comes back out again). It also doesn’t subject the parts to as much heat as hot salt bluing does. You end up with a very durable, high quality, blued finish. A lot of the bluing done on high end firearms is Express Rust Bluing. You can also “repair” damaged areas in already blued parts with this method as well.

This is the bluing formula I used for this project.

Like anything, there are some limitations to this process. You must be able to completely disassemble (not just field strip) the firearm you want to blue. Obviously, this process (though these rules apply to bluing in general) only works on metal parts. Also, Express Rust Bluing only works on steel. It will not work on stainless, aluminum, or other metals. In fact, trying to blue aluminum WILL result in disaster. Damage or destruction of your part and your bluing “tank” will be ruined. So if you are unsure of what metal your part is made from, check it with a magnet. If it sticks, you’re safe. While there are some stainless steels that are magnetic, the worst they will do is not blue. Lastly, any welded areas or spots will probably not blue evenly with the rest of the surface.

As I mentioned, you don’t need very much for equipment relatively speaking. You need a steel container big enough to hold the parts you want to blue-though you can work around that to a degree. At this time, my “tanks” are metal serving trays from a restaurant supply store. If you just want to blue handguns, you can even use an old pot (so long as it’s not aluminum). I have found that I could blue parts longer than would fit in my “tanks” with Express Rust Bluing as well-barrels for example. Obviously the part will hang out of the tank. But as long as you can re-orient the part to where it covers all of what was hanging out before, then this process will allow you to blue it. Obviously, you also need water and a heat source capable of boiling the water in whatever size container you want to use. You’ll need a carding wheel or brush, both being preferable. You need some kind of degreaser for the cleaning cycle. Depending upon what you’re specifically trying to blue, you may be able to just thoroughly clean the part with acetone. I use a heated solution of plain Dawn dish soap-which I will describe later. You’ll need the bluing formula itself. You’ll need some latex or rubber gloves so you can handle the parts without contaminating them with skin oils. Lastly, you’ll need some kind of water displacing oil. I use WD-40 for this because it’s readily available, but there are obviously other options for this if you prefer something else.

Now before we proceed, I should say a few words on safety. Always wear eye protection when performing the tasks described. Follow the instructions regarding the handling of the bluing formula. Read the safety portions of that BEFORE you begin, so if you have an accident you’ll already know what to do. Obviously, boiling the parts means you’ll be dealing with hot things. Also, this may come as a surprise but you should NOT plug your barrel when doing any kind of hot bluing. The heat from boiling will cause the air trapped in the bore to blow out the plugs. Obviously, this is not agreeable with it submerged in a tank full of hot liquid! Common sense needs to apply here. With that said, on to bluing!

A heated cleaning cycle is preferable to make sure the parts are completely free of oil.

The first, and arguably most important, step to getting a nice blued finish is the prep work. What you do for prep work really depends on what kind of finish you’re after. If you want a dull blue finish (like military arms have when they’re blued) then you can just sandblast with aluminum oxide and proceed. If you want something shinier, you’ll need to do some polishing. How much depends on how shiny you want the surface to be. But there is a trade off here: the more dull the finish, the more durable… the shinier, the less durable. Also, keep in mind that bluing (or any finish for that matter) will not hide flaws in the metal surface. If anything, it’ll make them stand out more. So do your prep work accordingly.

Next comes degreasing. Unless the parts you’re wanting to blue are pretty clean already, then you should clean them before the actual cleaning cycle. The cleaning cycle is to remove every bit of oil on the part, as even just the skin oils from your bare hands will ruin the finish. There are various solvents that you can use for this. I use Dawn dish soap and water because it’s cheap and readily available. A heated cleaning cycle works better, so that’s what I recommend you do. Basically, you want the cleaning cycle to be somewhere around 150-180 degrees. Hot but not boiling. Keep them in the tank for about 10 minutes. Once you’ve done cleaning, you can get rid of the solution as it’s best to use a fresh cleaner for each bluing session. If you only have one tank, you’ll obviously have to do this to proceed anyway.

Here are the parts in being boiled. You can get away with bluing parts that don’t fit all the way in the tank if you can make sure the portion outside of the tank is completely submerged when you rotate it.

After the cleaning cycle, rinse the parts off to remove any residual soap. Then put the parts in the tank to boil. This is where Express Rust Bluing gets a bit repetitive. Boil the parts for 2-3 minutes. Then apply the bluing formula. Then boil the parts for 2-3 minutes again, and so on until after the 3rd time you apply the bluing formula. Then boil the parts for 10 minutes, take them out and let them cool off. They’ll be nice and rusty at this point. Then polish the parts with the carding wheel and/or brush. That’s one bluing cycle. You need to do at least 3 cycles. You may want to do more to reach the color you want, and that’s perfectly fine. If you have parts with a bunch of nooks and crannies, you should heat the parts with a propane torch to 212 degrees after the final boil to ensure that all of the water is completely out.

This is what the part will look like before you card it the first time.
This is what it looks like after the first bluing cycle. It’s darker than when I started, but still a ways to go.

I should mention a few things about carding to be aware of. If you wish to use a carding wheel, they are typically not rated for more than 2000 RPM. So you probably can’t just throw one on your bench grinder. You also can’t substitute a carding wheel for a regular wire wheel, it’ll just take the bluing completely off-ruining your work. Also, I recommend having a carding brush as well. I find that there are some little spots that you just can’t reach with a carding wheel. A brush helps reach those. And then for the REALLY tight spots, have some extra fine grade steel wool (make sure you degrease it) on hand.

Here is the barrel after the 3rd cycle and final carding. Quite a difference!

After you have completed enough bluing cycles to get the color you’re after, then coat (or preferably dunk) your parts in water displacing oil. Again, I use WD-40 for this because it’s cheap and available. This is both to get any remaining moisture out and to protect the now-completely-oil-free part. Then let the parts sit for a day. After that, you can typically re-assemble your firearm. I say typically because if you’re like me, the next day you’ll find a spot that you missed or something will look splotchy. That’s where this process is really nice. Because all you have to do is go through cleaning, and a bluing cycle or two, and you’ll clean those areas right up.

Here is the finished product. I did that longer barrel to illustrate how to work around having a small tank. It came out great, with no uneven spots.

Express Rust Bluing is a good way for a hobbyist to blue their firearms at home. It does not require a whole lot of equipment and isn’t very difficult to do. If you’re doing smaller parts, you can even use old pots or pans for tanks. One bottle of the solution will last you through a bunch of bluing sessions. So really the process is pretty inexpensive. Cheap, minimal equipment, and simple are three terms that homebuilders like to hear. Express Rust Bluing offers hobbyists a way to finish firearms that all three terms apply to. Until next time, Happy Building!

Buy and Sell on GunsAmerica! All Local Sales are FREE!

About the author: Christopher Mace Christopher Mace enlisted in the US Army as an Infantryman in 2001. He served in the 82nd & 101st Airborne Divisions, with four deployments to Afghanistan & Iraq. Chris started hobby gunsmithing in 2005. After completing his service in 2010, he earned AAS degrees in Machining as well as Welding & Fabrication, and a Gunsmithing Technician Certificate from Trinidad State Junior College. Chris has taken several armorers courses on different firearms, and has built several different types of firearms. He has been collecting & shooting military firearms, old and new since he was 18. Chris enjoys repairing, customizing, building & assembling firearms, as well as different disciplines of competition shooting.

{ 10 comments… add one }
  • John Bloom November 17, 2021, 4:09 am

    There are uneven spots all over the long barrel…easily seen in the photo. I don’t know what you’re talking about.

  • Mark L Graf August 17, 2021, 6:04 pm

    I uae a cabinet blaster and use ALC Glass bead medium AC 60/120 grit, to strip the finishing off my firearms.
    Is using this method, do I need to do something else before the next step of cleaning?

    Thanks for your service Chris

  • Jim Titus March 1, 2021, 2:09 pm

    I’m wondering if you could help me with an 870 wingmaster–Thanks

  • Ray August 26, 2020, 6:36 am

    Why doesn’t the bore get rusty, through all the cleaning and bluing cycles?

  • Mark N. August 11, 2020, 1:31 am

    Then if you want to go REALLY old fashioned, get some Plum Brown, used in the muzzleloader days of yore. It calls for heating the part up to about 270 degrees, applying the product, then rinsing and washing in soap and water. Rinse, dry, repeat. It worked really well the one time I’ve tried it, the hard part being that the whole barrel did not fit inside the oven. The one thing I did wrong was that the oven mitts I used were not sufficiently degreased and it affected the outcome in a few spots.

  • Michael Remington August 10, 2020, 5:23 pm

    You cautioned against plugging the bore. What does this process do to the bore? I’m imagining horrible things—tell me I’m wrong!

    • Christopher Mace August 11, 2020, 12:49 am

      As long as you apply the water displacing oil and clean your bore afterwards, it doesn’t do anything to it. With this kind of bluing, you apply the bluing agent by hand. So it doesn’t go anywhere you don’t directly put it. If you don’t put bluing agent in your bore, it won’t get in there.

    • Ray Rojas April 21, 2021, 12:04 pm

      Michael Remington read the whole article again (slowly). Comprehension is key to understanding. Have a thesaurus, dictionary and google what befuddles you.

  • Jim Parker August 10, 2020, 5:53 am

    Great product. I recommend practicing on a few cheap guns before taking on grandad’s old 1873. With some practice you’ll find out little tricks that work. Here’s a hint: you cannot get the metal too clean. The cleaner the better. If you think you’re done washing the parts, do it one more time. Also be sure to keep copper away from your process, it will lend a brown finish instead of blue black color.

  • Tim Rorer August 10, 2020, 5:40 am

    I’ve only used the touch up product. I’ll give this a try. Great article, Chris!!

Leave a Comment

Send this to a friend